DE3718601C2 - - Google Patents

Description

The invention relates to a device for lifting at least one Stack of material from a base, in particular a stack of blanks from an intermediate or underlay in the tobacco industry, the genus specified in the preamble of claim 1.

Such a device emerges from DD-PS 159 617 and has one freely movable in all directions by an industrial robot guided gripper, at least one between the material stack and intermediate or insertable fingers of the gripper, at least a vertically movable one that can be placed on the material stack Clamping element and a control for the movements of the gripper depending on output signals from sensors.  

In addition, from DE-OS 28 28 860 a device for loading and Unloading of pallets that are caused by an industrial robot has freely movable grippers in all directions; at a In the first embodiment, this gripper is provided with a suction head, so that freight units, in particular parcels, i.e. uniform items, to lift off the pallet. In the embodiment according to FIG. 2 this gripper points in the gap between a package and his Base, generally a conveyor, insertable fingers on. However, this device is only for the removal of relatively heavy Parcels from a conveyor, provided that that the weight of the packages on the one hand and the frictional forces between the conveyor and the package, on the other hand, are large enough thus when the fingers of the gripper are inserted laterally into the gap between conveyor and package this is not laterally shifted but has such a great resistance to movement that the introduction the finger is possible in this gap.

Although there are similar problems with other types of material stacks, for example in the paper industry, but also in handling of foils, films and similar fabrics, will occur hereinafter referred to the tobacco industry, where not bundled Stack of blanks, especially packets or bundles cut, have to be moved; thereby the lack of cohesion of the individual blanks in the stack, the risk of damage to the sensitive cardboard surfaces and finally the risk of twisting of the edges represent the requirements that arise when developing a corresponding, automatic device for lifting and further transport of a stack of blanks must be considered.

It is also essential that in general on a pallet several stack of blanks arranged side by side in the horizontal direction are and form a "stacking layer" while in the vertical direction the different stacking layers, sometimes up to six or seven  Layers, each with an intermediate layer of paper, cardboard, wood or one Plastic film are separated from each other. So it must be guaranteed be that at least one stack of each stack layer is detected by the the associated intermediate layer can be lifted off and transported onward, without the risk of damaging the sensitive, individual Blanks exist.

And finally, each blank stack has to be during such a gripping process still be stabilized so that not individual blanks can slip out, or not the entire stack can slip.

The invention is therefore based on the object of a device for Lifting off at least one stack of material from a base, in particular a stack of blanks from an intermediate or underlay in the tobacco industry to create the specified genus which the non-slip gripping of stacks made of easily deformable materials guaranteed.

This object is achieved by the in the characterizing part of the specified features solved.

Advantageous embodiments are characterized by the features of the subclaims Are defined.

The advantages achieved with the invention are based on the following mode of operation: In the tobacco industry, pallets with parcel or Package blanks delivered by truck, during transport usually two pallets are stacked on top of each other. The pallets are lifted off the trucks individually, so that the for protection  serving plastic films can be removed by hand. As in the DE-PS 35 19 580, but also described in the earlier application P 36 27 670.7-23 will be the "stripped" pallets from a driverless transport system recorded and in the access area of a specific embodiment of an industrial robot, namely a portal robot. The gripper of this industrial robot is brought up to the pallet and positioned on a blank stack. After the gripper at least has picked up a stack, the industrial robot removes the loaded one Gripper, so that there is no risk of collision with further transport other blank stacks or other pallets.

The industrial robot with the loaded gripper is attached to the one to be loaded Processing machine brought up and the stacks deposited, so that the Individual cuts of each stack and into cigarette or container boxes can be folded.

The pallets are loaded manually by some cut suppliers; in addition, the pallets are shifted during the cutting process, so that you don't have a repetitive, consistent positioning the stack can expect; additional position deviations occur when weaning of the pallets. The dimensions of the pallets are also included large tolerances. Entering fixed approach positions for the Grippers, for example in the manner of a "teach in", would therefore cause collisions with the Stack and damage the blanks so that the safe Access becomes practically impossible. So that the industrial robot is in can adapt certain changed stack positions and the safe Gripping is possible, the gripper with sensors for position detection and distance measurement, so that the exact location and proper Form of each stack determined and thus each stack with the required Care can be taken and lifted off.

In principle, the sensors can work inductively, capacitively and with ultrasound; capacitive sensors are too small for this application Sensing range, ultrasonic sensors have one too Large switching distance and inductive sensors are ruled out for non-metal. According to a preferred embodiment, sensors are therefore optical Reflex sensors are used, i.e. light-emitting diodes with photo transistors. The  Light routing for the reflex sensors takes place via fiber optic cables to this Way to keep the size of the gripper small.

The processors currently being used in the tobacco industry processing machines process about 400 cuts per minute; a blank Stack contains about 500 blanks. To stop processing Avoiding the machine must take into account the route of the industrial robot the gripper will be able to stack three complete blanks to be transported in one operation, namely from the start at the processing machine, about the movement to the pallet, positioning the gripper, Gripping the or each stack, returning to the processing machine and unloading.

The gripping required because of the speed of the processing machine however, from three stacks in one work cycle requires further design specifications; because there are usually eleven stacks on a pallet side by side, so that when removing three stacks at a time only two pairs of stacks remain on each stack line. For this reason the gripper can be designed so that two stacks can be transported can. These requirements can be met by designing the gripper accordingly the required number of elastically deformable fingers, pressure and Clamping elements, as well as the corresponding sensor equipment taken into account will.

Taking into account the performance, especially the load capacity of commercially available industrial robots on the one hand and the weight of approx. 7.5 kg for three stacks, on the other hand, the gripper may only use one have a relatively light weight; this is taken into account by the fact that largely only light, strip-shaped components for the supporting structure of the gripper in connection with light sensors and small clamping elements can be used, which are operated pneumatically.

The elastically deformable fingers are made by means of a feed cylinder moved relative to the gripper and thereby between the bottom cut of the Stacked and intermediate or underlay inserted.  

According to a preferred embodiment, each finger has a wedge shape with a rounded shape Tip, which is expediently still ground to the Insert your finger between the bottom cut of the stack and to simplify the underlay or intermediate layer. In addition, the finger must Retraction highly flexible, but on the other hand be stiff enough to do that Record stack weight and additionally apply a clamping force can. The finger can be made of sheet steel with the desired properties be manufactured.

The moment of inertia increases due to the wedge shape of the tips of the fingers down to the peaks. As a result, despite the same material thickness An increase in flexibility towards the tips is achieved while at the rear the stiffness increases in the bearing area.

To the gripper the desired despite the desired, low weight To give rigidity, the load-bearing parts are supported by box profiles or Angle profiles formed.

The pressure elements, in front of the clamping elements, on the top cut put on each stack lead to stabilization of the stack during the retraction of the fingers, so that not individual Cuts can slip out, or not the entire stack slips; in addition, at least short stacks will be attached to theirs Faces fanned away from the pressure elements, thereby retracting of the finger in the resulting gap between the lower or Liner and the bottom blank of the stack is facilitated.

The sensors attached to the gripper recognize breakpoints and errors, d. that is, the gripper is not only by fixed coordinates, but also controlled by the geometry of the stack to be gripped. Only when that Deviations in the geometry from a predetermined target value of the stack If the pallet exceeds a certain tolerance range, an alarm signal is issued submitted to call the operator to make the mistake fix and start the process again, especially the gripper to the Can move stack on the pallet.  

In particular, deviations in the position of the Pallet and thus the stack, shifted individual stacks as well as extremely high ones or extremely low stacks, which are no longer possible due to the gripper can be detected correctly.

If a stack layer has already been completely cleared, must be used as next the liner must be removed before at least one stack of the next stack position can be detected. For this purpose the gripper provided with suction heads, which are located on its back. By a Swiveling movement of the gripper from the normal position by 90 ° can suction heads placed on the intermediate layer and then with negative pressure be opened so that the intermediate layer adheres to the suction heads; the Intermediate layer can then by means of a kind of "peeling movement" from the next Stack position can be deducted.

To supply the suction heads with negative pressure, either negative pressure is used line in the gripper or the existing one in the gripper Compressed air converted to negative pressure using a jet pump.

The invention is described below using exemplary embodiments under Be access to the accompanying schematic drawings explained in more detail. It demonstrate

Fig. 1 is a perspective view of a pallet with five sheets of blank stacks and a device for lifting off and further transporting at least one stack,

Fig. 2 is a perspective view of a gripper of the apparatus,

Fig. 3 is a perspective view of three horizontally alongside one other arranged stacks of blanks for hinge eyelid (HL) packs with the directions of action of the associated sensors,

Fig. 4 is a perspective view of the gripper in the starting position at the corner of a blank position for the detection of three blank stacks,

Fig. 5 is a perspective view of the gripper when moving the Grei fers in the direction of the front end wall of the stack,

Fig. 6 is a perspective view of the gripper during the lowering of the pressure elements,

Fig. 7 is a perspective view of the gripper during the insertion of the fingers into the gap between the stacks and the intermediate layer,

Fig. 8 is a section through the gripper with a representation of a finger resting on the intermediate layer and in the inserted position of the finger, and

Fig. 9 shows the position of the gripper when lifting the intermediate layer.

The apparent from Fig. 1, generally indicated by the reference numeral 10 device is used for lifting and transporting two or three stacks of blanks, each arranged in individual layers on a Pa 12 . In Fig. 1, five stack layers 14 are shown, each consisting of three stack rows 16 , each with eleven individual stacks 18 and separated from one another by intermediate layers 15 made of paper, cardboard, wood or plastic.

In the embodiment described here are blanks for hinge-lid packets, which must be taken into account in the spatial arrangement of the sensors 10 of the device 10 , which is yet to be explained. In the same way, however, other packets and pack blanks can also be processed if this is taken into account by arranging the sensors accordingly.

The device 10 has a portal 20 for moving a conventional industrial robot 22 with a plurality of joints for the various arms 24 , 26 , 28 of the industrial robot 22 , so that the tool to be handled by the industrial robot 22 , namely a gripper 30 to be explained below, can be continuously adjusted in all directions.

The gripper 30 shown in FIG. 2 on a larger scale has an essentially box-shaped frame, the side walls of which, as far as possible, have been left out for reasons of weight saving, that is to say are essentially formed by webs, angle profiles or box profiles.

The industrial robot 22 has a vertical pin 32 shown in FIG. 1, which is attached to a crossbar (carrying crossbar) 34 from a box profile of the gripper 30 . This crossbar 34 is rigidly connected to the load-bearing parts, in particular the side walls 36 , 44 shown in FIG. 2. The right side wall 44 of the gripper 30 as shown in FIG. 2 is only partially shown.

The side walls 36 , 44 are connected to one another by the rear crossmember 54 and the end crossmember 48 . Between the two side walls 36 , 44 there is a slide 38 made of a square tube with three vertical supports 40 which support a floor 42 . The carriage 38 is mounted on the guide rails NEN 41 and 43 between the rear cross member 54 and the front cross member 48 ver mobile. The slide 38 is connected to the pneumatic cylinder 47 via the piston rod 46 .

In the illustrated embodiment, three pressure elements 50 are attached to the end crossmember 48 . The pressure elements 50 are mounted vertically displaceable bar. The displacement takes place against a compressive force that can be applied by a spring 51 , for example a coil spring or an air accumulator. Three pneumatically actuated clamping elements 52 are attached to the web 34 .

On the rear crossmember 54 two suction heads 56 are attached in the illustrated embodiment, which can be acted upon by means of a vacuum line (not shown); as an alternative to this, it is also possible to convert the compressed air already present in the gripper 30 into negative pressure for the application of the suction heads 56 by means of a jet pump.

In the embodiment shown, the bottom 42 of the gripper 30 is provided with three flat fingers 58 facing the pressure elements 50 , which have a wedge shape with a rounded and flattened tip. These fingers 58 are integrally formed with the bottom 42 and consist of an elastically deformable material with a high restoring force, in particular Fe derstahl.

As an alternative to this, the fingers 58 can also be made from spring steel alone and connected to the floor 42 in a suitable manner.

The control of the gripper 30 is carried out with the aid of sensors, the spatial arrangement and function of which will be explained below with reference to FIGS . 2 and 3.

A cross bar 60 , on which three sensors 62 are mounted, is arranged between the two side walls 36 , 44 above the end crossmember 48 . These sensors 62 (see also FIG. 3) measure the distance to the uppermost blank of each stack when the gripper is lowered onto a stack layer 14 by measuring the decreasing distance of the spring-loaded pressure elements 50 when the gripper 30 is placed on it. As a result, the force with which the pressure elements 50 press on the stack is measured indirectly via the characteristic curve of the springs 51 . They generate a corresponding, analog signal, which is passed on to a threshold switch (not shown).

On the outside of the side wall 44 a protruding Winkelpro fil 64 is attached, which carries a sensor 66 arranged in the horizontal direction (see FIG. 3) for determining the distance between the side surface of a stack and the gripper 30 .

Another, U-shaped crossbar 69 is attached to the outer sides of the two side walls 36 , 44 approximately below the crossbar 34 and carries two rows of three sensors each. A first row of sensors 68 horizontally measure the distance between the sensor and the front end wall of the three blank stacks 18 (see FIG. 3), while three downward sensors 70 measure the distance to the fingers 58 below and thereby detect a deformation of the fingers 58 .

On the U-shaped crosspiece 69 there are also two further sensors 72 which are assigned to the two left sensors 68 , 70 and measure the distance perpendicular to the beveled side surface of the two right blank stacks 18 at an angle at the same height as the sensor 66 .

If three stacks 18 are to be detected simultaneously, the right sensor 72 as shown in FIG. 3 is queried in order to detect the right edge of this row of stacks; If, starting from the left-hand section stack 18 , whose side surface is scanned by the sensor 66 , only two stacks 18 are to be detected, only the sensor 72 is queried, which is shown in FIG. 3 on the middle blank - Stack 18 is located.

Finally, there is another sensor 74 on the rear crossmember 54 between the two suction heads 56 , which - with the appropriate position of the gripper 30 - determines the distance to the intermediate layer 15 , as will be explained below.

Optical reflex sensors are used as sensors, that is to say light emitting diodes (transmitters) with photo transistors (receivers), since only these commercially available sensors have the required switching range with adequate accuracy. In order to keep the gripper 30 compact and light, the light is guided for the sensors via fiber optic cables.

The analog output signals of the sensors are digitized in each of the downstream threshold switches; these threshold switches are coupled to a logic unit which performs a pre-evaluation of the signals and provides the result of the control circuit of the industrial robot 22 as a return signal.

This control circuit must also directly or indirectly through another Logic unit the different sensor groups depending on the movement phase switch that, under certain, previously defined conditions, the current Movement aborted or a new movement or after a query block grasping be initiated. Likewise, the robot controller becomes one Alarm situation communicated as a return signal.  

The process will be described below with reference to FIGS. 4 to 7; the gripper 30 is first brought into the starting position shown in FIG. 1 by means of the industrial robot 22 , for example, in a position above the upper stacking position 14 on the pallet. For the different stacks to be gripped, this starting position is permanently preprogrammed in the robot controller by means of its coordinates, i.e. the gripper 30 automatically moves to a position in which it is relatively close to the stacks 18 to be detected, but even in the event of tolerance fluctuations in the Position of the pallet 12 and thus the stack 18 there is still no risk of contact between the stack 18 and the gripper 30 .

As can be seen from FIG. 1 and in particular from the enlarged illustration in FIG. 4, in this position the pressure elements 50 are located above the upper blanks of each stack, while the sensor 66 is opposite the side wall of a corner stack, specifically the side wall, which is on the left side in the direction of displacement of the gripper 30 to be explained.

Starting from this starting position, the further control takes place by means of the output signals of the various sensors, ie the gripper 30 is controlled not only by fixed coordinates, but also by the geometry of the blank stack 18 . An alarm signal is only given when the deviations in the geometry from predetermined target values of the blank stacks on the pallet 12 exceed a certain tolerance range. The operator must then correct the error, for example move the pallet a little ver, and start the program again, whereby the gripper 30 is moved up to the stack again.

If three stacks 18 are now to be grasped and lifted, the sensor 66 is first queried in order to bring the gripper 30 into the desired position, ie the gripper 30 arranged over the blank stack 18 becomes in the direction shown in FIG. 4 of arrow A, that is to say shifted in the direction of a stack row 16 , until the sensor 66 detects the desired distance and thereby ascertains a precisely defined position of the gripper 30 in relation to the three stacks 18 .

Starting from this position 2 , which can be seen in FIG. 5, the gripper 30 is then moved by means of the industrial robot 22 in the direction of the arrow B in FIG. 5, that is, towards the front end face of the blank stack 18 until the sensors 68 detect a precisely defined distance between Grei fer 30 and the end face of the blank stack 18 to be gripped. In this position, which can be seen from FIG. 6 as position 3 , the Grei fer 30 is stopped.

Now the entire gripper 30 is moved vertically downwards in the direction of arrow C of FIG. 6, whereby the fingers 58 are placed on the intermediate layer 15 . When placed on the intermediate layer 15 , the fingers 58 are bent slightly upwards. The change in position of the tips of the fingers 58 is detected by the sensors 70 . At the exact height of the stacks 18 , the pressure elements 50 are simultaneously pressed onto the upper blanks of the blanks and in this way fix the position of the blanks. In addition, the blanks on the end faces are fanned out somewhat. The sensors 62 serve to control the height of the individual cut stacks 18 and to monitor the spring travel of the compressed pressure elements 50 . With knowledge of the spring characteristic can then be inferred at a certain deflection on the compressive force on the stack. The movement in the direction of arrow C is therefore also controlled in a force-dependent manner, which is important in order to ensure a minimum force with which the stack 18 is prevented from slipping during the gripping process. The movement of the gripper 30 in the direction of the arrow C is interrupted when the sensors 62 signal the target values and the sensors 70 have indicated a minimum deflection of the fingers 58 , but at the latest when the maximum deflection on a finger, indicated by a sensor 70 is reached, or the maximum pressure force on one of the pressure elements 50 , indicated by a sensor 62 , occurs.

Now the carriage 38 is moved in the direction of arrow D in Fig. 7, that is, in the horizontal direction, so that the fingers 58 are inserted into the gap between the intermediate layer 15 and the bottom blanks of the three stacks. Are the fingers 58 as far below the cut stacks 18 , as required, the clamping elements 52 are actuated to clamp each of the three stacks 18 between its clamping element 52 on the one hand and its finger 58 on the other hand and fix it.

After the three stack 18 by the clamping elements 52 and the fingers have been fi xed 58, can the three sheet stack lift 18 by a entspre sponding movement of the industrial robot 22 and set to the processing, namely, a packaging machine, transport. There, the gripper with the stacks 18 is placed on the storage surface. The stacks 18 are again forcibly fixed by the pressure elements 50 . Then the clamping elements 52 are raised and the fingers 58 are then pulled out from under the stacks 18 , so that after the gripper 30 has moved away, the three stacks 18 are free and can be processed.

. If, in the manner shown in Figure 1 starting position in three such From three stack 18, for a total of nine stacks 18 runs advantage transported away, so only two stack 18 left; the same sequence then follows, but under the control of the sensor 72 , which, as shown in FIG. 3, is located on the middle stack 18 in order to detect the right edge of this “stack row”.

Fig. 8 shows on an enlarged scale two stack-to-stack 18 arranged one above the other, which are separated by the intermediate layer 15 ; the front end of the deformable finger 58 lies on the relatively rigid intermediate layer. In the broken line, the carriage and the finger 58 are pushed under the blank stack 18 .

If an entire stack layer has been cleared, the intermediate layer 15 is exposed and must be removed. For this purpose, the gripper 30 by means of the industrial robot 22 rotates 90 ° into the position shown in FIG. 9 so that the suction heads 56 are directed downward. Controlled by the output signal of the sensor 74 , the gripper 30 is now moved downward until the suction heads 56 rest on the intermediate layer 15 . Now the suction heads 56 are acted on by vacuum so that they adhere to the intermediate layer. By means of a corresponding movement of the industrial robot 22 , the intermediate layer 15 can then be lifted off from the next stacking layer 14 in a kind of "peeling movement" and, for example, be put away as waste. The next stack layer 14 is now exposed, so that the individual stacks 18 can be sequentially detected, lifted off and transported away in accordance with the sequence described.

The structure described, in particular the spatial arrangement described the sensors, is designed for gripping parcel blanks, namely of hinge-lid blanks. In the same way, you can Appropriate adjustment of the position of the sensors, however, other packets too cuts or bundle cuts can be recorded.

Claims (9)

1. Device for lifting at least one stack of material from a base, in particular a stack of blanks from an intermediate or base in the tobacco industry,

• a) with a gripper ( 30 ) which is freely movable in all directions by an industrial robot ( 22 ),
• b) with at least one finger ( 58 ) of the gripper ( 30 ) which can be inserted between the material stack ( 18 ) and the intermediate or underlay ( 15 ),
• c) with at least one clamping element ( 52 ) which is movable in the vertical direction and can be placed on the material stack ( 18 ), and
• d) with a control for the movements of the gripper ( 30 ) as a function of output signals from sensors,

characterized by the following features:

• e) at least one pressure element ( 50 ) is provided, which is placed on the or each material stack ( 18 ) in front of the clamping elements ( 52 ); and
• f) the or each elastically deformable finger ( 58 ) is movable in the insertion direction relative to the pressure element ( 50 ) or the pressure elements ( 50 ).

2. Device according to claim 1, characterized in that three clamping elements ( 52 ), three fingers ( 58 ) and three pressure elements ( 50 ) are provided for gripping three material stacks arranged next to one another ( 18 ). 3. Device according to one of claims 1 or 2, characterized in that the pressure element ( 50 ) or the pressure elements ( 50 ) is resiliently GE or are. 4. Device according to one of claims 1 to 3, characterized in that a sensor ( 66 ) detects the distance between the gripper ( 30 ) and the side wall of a material stack ( 18 ). 5. Device according to one of claims 1 to 4, characterized in that sensors ( 70 ) detect the vertical distance between the gripper ( 30 ) and the or each finger ( 58 ). 6. Device according to one of claims 1 to 5, characterized in that in material stacks ( 18 ) with tapered end walls Sen sensors ( 72 ) for detecting the distance between the gripper ( 30 ) and these tapered end walls are provided. 7. Device according to one of claims 1 to 6, characterized in that on one side of the gripper ( 30 ) suction heads ( 56 ) are provided for the He the intermediate layer ( 15 ). 8. The device according to claim 7, characterized in that the suction heads ( 56 ) is assigned a further sensor ( 74 ) for detecting the distance between the intermediate layer ( 15 ) and the suction heads ( 56 ).